1. Field
The disclosed concept relates generally to electronic trip units, and in particular, to electronic trip unit interfaces operable to program settings of electronic trip units. The disclosed concept also relates to circuit interrupters including an electronic trip unit. The disclosed concept further relates to methods of setting trip unit settings of electronic trip units.
2. Background Information
Circuit interrupters, such as circuit breakers, are generally old and well known in the art. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. In small circuit breakers, commonly referred to as miniature circuit breakers, used for residential and light commercial applications, such protection is typically provided by a thermal-magnetic trip device. This trip device includes a bimetal, which heats and bends in response to a persistent overcurrent condition. The bimetal, in turn, unlatches a spring powered operating mechanism, which opens the separable contacts of the circuit breaker to interrupt current flow in the protected power system.
Industrial circuit breakers often use a circuit breaker frame, which houses a trip unit. See, for example, U.S. Pat. Nos. 5,910,760 and 6,144,271. The trip unit may be modular and may be replaced, in order to alter the electrical properties of the circuit breaker.
It is well known to employ trip units which utilize a microprocessor to detect various types of overcurrent trip conditions and provide various protection functions, such as, for example, a long delay trip, a short delay trip, an instantaneous trip, and/or a ground fault trip. The long delay trip function protects the load served by the protected electrical system from overloads and/or overcurrents. The short delay trip function can be used to coordinate tripping of downstream circuit breakers in a hierarchy of circuit breakers. The instantaneous trip function protects the electrical conductors to which the circuit breaker is connected from damaging overcurrent conditions, such as short circuits. As implied, the ground fault trip function protects the electrical system from faults to ground.
The earliest electronic trip unit circuit designs utilized discrete components such as transistors, resistors and capacitors.
More recently, designs, such as disclosed in U.S. Pat. No. 4,428,022; and U.S. Pat. No. 5,525,985, have included microprocessors, which provide improved performance and flexibility. These digital systems sample the current waveforms periodically to generate a digital representation of the current. The microprocessor uses the samples to execute algorithms, which implement one or more current protection curves.
Electronic trip units have various settings which can be adjusted to change the behavior of the electronic trip unit. Several known electronic trip units include an interface panel which is used to adjust the settings of the electronic trip unit. One known electronic trip unit includes an interface panel having five rotary switches, two light emitting diodes (“LEDs”), and one test port which are used to adjust the settings of the electronic trip unit. Additionally, an external module is required to read cause of trip information from the electronic trip unit. However, each component on the electronic trip unit interface panel, as well as the external module, increase the cost of the electronic trip unit.
There is room for improvement in electronic trip units.
There is also room for improvement in circuit interrupters.
There is also room for improvement in methods of setting trip unit settings of electronic trip units.